Counter-flow fireplace

ABSTRACT

A prefabricated fireplace assembly is constructed as a doublewalled structure defining an open-front hearth and a dome portion terminating at its upper end in a smoke pipe adapted to cooperate with counterflow chimney of the type having concentric ducts for drawing in cooling air and discharging warmed air. A hood-like baffle surrounding the front and sides of the dome portion and disposed in the space between the double walls directs cooling air from the chimney over internal surfaces to be cooled and back to the chimney.

United States Patent 1 1 1111 3,724,443 Carson 1451 Apr. 3, 1973 [541 COUNTER-FLOW FIREPLACE 2,821,975 2/1958 Thulman ..l26/l20 1 3,094,980 6/1963 lnabnit ..l26/l2l [751 Invent W Savannah 3,190,281 6/1965 Northwood ..l26/307 R x [73] Assignee: Martin Stamping 8: Stove Company,

Huntsville Primary Examiner-William F. O'Dea Assistant Examiner-Peter D. Ferguson Flledi g- 1971 Attorney-Cushman, Darby & Cushman 21 .A 1.No.: 173 590 1 pp 57 ABSTRACT Rented Appliuflm Data A prefabricated fireplace assembly is constructed as a [63] continuatiomimpm f Sen No 8469, Aug 1, double-walled structure defining an open-front hearth 1969, pat 3,601,111 and a dome portlon termmatmg at its upper end 1n a smoke pipe adapted to cooperate with counterflow [52] us Cl 126/121 chimney of the type having concentric ducts for draw- [51] Int Cl 4b 7/00 ing in cooling air and discharging warmed air. A hood- 58] Fieid 237/51 like baffle surrounding the front and sides of the dome a c portion and disposed in the space between the double 237/55 walls directs cooling air from the chimney over inter- [56] R f C1 d nal surfaces to be cooled and back to the chimney;

e erences 1 e 6 Claims, 20 Drawing Figures UNITED STATES PATENTS 2,634,720 4/1953 Thulman ..l26/307 R PATENTEDAPRS I973 3,724,443

' SHEET 1 BF 6 INVENTOR l #2 Male 6. (00am ATTORNEYS PAIENTEDAPR 3 m3 3. 724,443

. ATTORNEYS PATENTEDAPRIB 1975 saw 3 BF g;

I Q INVENTOR.

W; 75/? 6. Chara/v PATENTEDAPRB I975 SHEET l 0F 6 3 L-Ing IN VEN TOR.

COUNTER-FLOW FIREPLACE This is a continuation-in-part of application, Ser. No. 846,911, filed Aug. 1, 1969, now U.S. Pat. No. 3,601,117.

This invention relates to fireplace constructions and in particular to fireplace assemblies which are prefabricated to be installed into the buildings of which they are to become a permanent part.

A major problem facing those designing fireplace assemblies of the above-mentioned type is to provide a fireplace in which the exterior surfaces are sufficiently cooled so that the temperature of the fireplace will not endanger the surrounding structure. Furthermore, the fireplace .must be designed so that it will not direct a significant amount of heat into the room in which it has been placed so as not to be uncomfortable when used with a central heating system.

In U.S. Pat. No. 2,821,975 to Robert K. Thulman there is described a fireplace construction in which cool ambient air passes down a counter-flow chimney, around the firebox and associated dome and back up the chimney. The construction provides a plurality of thermo-syphonic paths to reduce temperatures on the surface of the outer casing of the fireplace unit, but is relatively complex in that at least two concentric casings are provided around the firebox in order to provide the necessary paths for airflow. This results not orily in a complex assembly, but one of extreme weight and bulk.

It is therefore an object of this invention to simplify the construction of fireplace assemblies by providing a single housing around the firebox together with a novel arrangement of internal air passages to achieve improved cooling with ambient air supplied from a counterflow chimney.

In accordance with the principles of the present invention the air passages within the double-walled fireplace assembly provide for the closed cycle flow of cooling air downwardly from the inlet air duct of a counter-flow chimney, under the floor of the hearth or firebox and back up to the discharge duct of the chimney. The air may take any of several flow paths as it moves downwardly and upwardly under the influence of thermosiphon effects and internal structure.

In a preferred embodiment the incoming air first passes downwardly through front and side spaces defined between the outer wall and a baffle spaced from the dome portion of the inner wall. The air from the front space mingles with the air from the side spaces and then flows downwardly along each side wall, then horizontally and rearwardly under the hearth floor. At the rear of the hearth floor the air passes into a vertical duct defined between the inner and outer walls. The air flows up this duct to the exhaust duct of the chimney, some of the air diverting at the top of the firebox to flow over the dome betweenthe dome and V the aforesaid baffle and upwardly to the exhaust duct of the chimney.

Another feature of the invention relates to the useof thermal insulation to assure that a thermosiphon efiect will cause the desired air flow. Broadly speaking, the insulation is provided on the outer surface of the up air passages and on the inner surface of the down air passage. With this arrangement the entering air will be relatively insulated from the heat of the inner wall while the up air will be in contact with and heated by the inner wall, thereby creating syphonic flow. In the preferred embodiment described above insulation is provided on the outer surface of the baffle on the outer surface of each firebox side wall and on the inner surface of the outer back wall.

Yet another feature of the invention is the provision of a novel shield arrangement in the firebox adjacent the side walls thereof for the purpose of preventing excessive side wall temperature. This reduces thermal damage to the side walls and to the insulation on the side walls. In the preferred embodiment the shield takes the form of a vertical plate spaced slightly from each side wall of the firebox so as to define a space which is open at the front to room air and which is open at the top to the interior of the dome.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a front elevational view, partially broken away, of a fireplace embodying the principles of the present invention;

FIG. 2 is a plan view of the fireplace of FIG. 1, partly broken away along the line 2- 2 of FIG. 1;

FIG. 3 is a sectional view taken on the line 3-3 of FIG. 1;

FIG. 4 is a front elevation of another embodiment of the fireplace assembly constructed according to the principles of this invention;

FIG. 5 is a side elevational view of the embodiment illustrated in FIG. 4;

FIG. 6 is a rear perspective view of the preferred embodiment illustrated in FIG. 4 with-the side walls and the rear wall of the housing removed;

FIG. 7 is a top elevational view of the preferred embodiment illustrated inFIG. 4;

FIG. 8 is a fragmentary front perspective view of the preferred embodiment illustrated in FIG. 4 in which the front wall and a side wall of the housing have been removed;

FIGS. 9-l2 are sectional plan views of an open front fireplace constructed according to the principles of this invention illustrating various air fiow patterns;

FIGS. 13-l6 are sectional plan views of an open-end fireplace, that is, a fireplace open on two adjacent sides, illustrating various air fiow patterns; and

FIGS. 17-20 are sectional plan views of a fireplace open on two opposite sides illustrating the various airflow patterns.

DETAILED DESCRIPTION FIGS. 1-3 illustrate a preferred construction of a double-walled fireplace assembly 110. The assembly is constructed, broadly, of an inner wall assembly which defines a unitary firebox 112 and dome 114, and an outer cabinet structure 116 surrounding the firebox and dome. The inner assembly includes a horizontal hearth floor 118, a vertical rear wall 120 and two rearwardly converging vertical side walls 122 and 124 which seal with the rear wall 120 and extend beyond the latter ina rearward direction. The dome 114 of the inner assembly includes an upwardly and rearwardly inclined front wall 126 which extends from the upper edge of a hearth opening 128 to a horizontal top wall 130. The remainder of the dome 114 is defined by the vertical rear wall 120 and by upwardly and inwardly inclined side walls 132 and 134 which extend from the firebox side walls 122 and 124, respectively, up to the top wall 130. The forward edges of the dome side walls 132 and 134 close with the front wall 126, and the rear edges abut and close with the vertical rear wall 120.

A vertical smoke pipe 136 is secured in an aperture in the top wall 130 of the dome and is concentric with the lower end of a counter-flow chimney 138. A damper 140 is positioned in the lower end of the pipe 136. The chimney assembly 138 includes three concentric ducts the innermost duct 142 being concentric with and connected to the smoke pipe 136. The two outer ducts 144 and 146 define an outer annular passage 148 adapted to draw in cool ambient air and an inner annular passage 150 adapted to exhaust warmed cooling air to the atmosphere.

The outer cabinet structure 116, which surrounds the firebox 1 12 and dome 114 assembly, includes a vertical rear wall 152 which is spaced rearwardly from the inner rear wall 120 and which is sealed to the rear edges of the firebox side walls, 122 and 124, thereby defininga vertical passage. 1S4 extending up the back of the firebox 112. The cabinet 116 also includes vertical side wall portions 156 and 158 extending parallel to the firebox side walls 122 and 124 and sealing with the cabinet rear wall 152. Adjacent the dome 114 the cabinet 116 has upwardly and inwardly inclined side wall portions 160 and 162 and an upwardly and rearwardly inclined front wall portions l64. Vertical front wall sections 166 surround the hearth opening and seal with the cabinet side walls. This arrangement provides a vertical air passage 168 adjacent each side of the firebox, each passage 168 being formed by the respective firebox side wall 122 or 124, the respective cabinet side wall 156 or 158, an edge portion of the cabinet rear wall 152 and the respective front wall section 166.

The cabinet structure -1 16 also includes a horizontal bottom wall 170 disposed below the hearth floor 118 and sealing along its edges with the lowermost front wall section 116, the cabinet side walls 156 and 158 and the cabinet rear wall 152. These walls thereby define a space 172 which communicates at the rear of the assembly with the passage 154 and at the sides of v the assembly with the passages 168.

A hood-shaped baffie 174 is provided adjacent the dome 114 and between the dome 114 and the cabinet 116 to define an outer passage 176 communicating with the annular air inlet space 148 and an inner space 178 communicating with the annular air outlet passage 150. The baffle arrangement includes an inclined front wall portion 180 having a lower edge closing with the lower portion of the front wall 126 of the dome (that is, closing with the top. edge of the firebox) and extending upwardly and inwardly to a top wall portion 182. Two inclined side wall portions 184 and 186 have lower edges closingwith the lower portion of the dome side walls 132 and 134 and extend upwardly and inwardly to the top wall portion 182. The rear edges of the side wall portions 184 and 186 lie in the same plane as the rear edges of the dome side walls 132 and 134 and seal with the cabinet rear wall 152. The rear passage 154 thereby opens at its upper end into the enlarged somewhat annular space 178 defined between the baffie arrangement 174; the dome 114 and the upper part of the wall 152.

The top wall 182 of the baffie arrangement is provided with an opening which receives the lower end of the intermediate duct 144 of the chimney assembly 138, so that air flowing into the space 178 from below may pass into the exhaust passage 150. The lower end of the outermost duct 146 of the chimney assembly 138 is received within an opening in a horizontal top wall 188 of the cabinet 116 so that the air inlet passage 148 is in direct communication with the space 176.

In order to assure that the incoming cooling air does not become heated too soon and thereby alter or destroy the desired thermosiphon effect, thermal insulation is provided on the hot side of the down air passages. As shown, layer of insulation 190 is secured to the outer surfaces of the walls 180, 182, 184 and 186 of the baffie 174 and further layers 192 and 193 to the outer surface of the firebox side walls 122 and 124 and to the lower surface of the hearth floor, respectively. The rearwall of the firebox 112 and of the dome 114 are free of insulation, but the rear wall 152 of the cabinet 116 is covered with an inner layer of insulation 194 to reduce heat transmission to the exterior'of the fireplace assembly. A further piece of insulation 196 is provided adjacent the inner surface of the cabinet front wall 164 just above the hearth opening 128.

Overheating of the firebox side walls .122 and 124 and thermal damage to the insulation 192 is prevented by two vertical shields 198 each of which is disposed within the firebox 112 and positioned close to and parallel to one of the side walls 122,124. The lower edges of the shields 198 are supportedon the hearth floor 118. I

OPERATION OF EMBODIMENT 0 FIGS. 1-3

During operation of the fireplace assembly the flow path of atmospheric air is downwardly through the annular chimney passage 148, downwardly over the baffle 174, downwardly along the sides 122 and 124 of the firebox 112, underneath the hearth floor 118, up along the back of the firebox 112 and'up the annular chimney passage 150. Specifically, the entering air flows downwardly over the baffle front wall and simultaneously downwardly over the baffie side walls 184 and 186, the insulation on these walls-preventing any significant increase in the temperature of the air. At the level of the upper edge of the firebox opening 128 the air which is moving downwardly over the front wall 180 of the dome 1 14 flows laterally, mixes with the air flowing downwardly over the side walls 184 and 186 and passes into the passages 168 defined between the firebox side walls 122,124 and the cabinetside walls 156,158. At the lower ends of the passages 168 the air flows inwardly under the hearth floor into the space 172 and then rearwardly to the lower end of the vertical passage 154 defined between the firebox rear wall 120 and the cabinet rear wall 152. At this stage the air is still relatively cool as a result of the insulation on the hot side of the passages 176 and 168 and on the hot side of the space 172.

The air is heated rather rapidly as it passes up the back of the firebox, thereby effecting a thermosiphon action. At the level of the dome 114 some of the air continues to flow upwardly along the firebox rear wall 120. The remainder of the air moves forwardly and then upwardly in contact with the front and side walls 126, 132 and 134 of the dome 114, that is, through the somewhat annular passage 178. Just above the top wall 182 of the baffle 174 this air mixes with the air which passed along the upper part of the wall 120, and the combined flows pass into the annular chimney passage Also during operation of the fireplace assembly room air will pass rearwardly into the spaces between the two vertical shields 198 and the respective side walls 122,124, then upwardly into the interior of the dome 114 and finally up through the smoke pipe 136. This assists in cooling the side walls 122,124 which are insulated on the opposite sides and therefore susceptible to overheating.

While the air flow in the preferred embodiment is as described above, the same basic double-walled structure and hood-type baffle 174 over the dome 114 may be employed with slight modifications to achieve other suitable air flows. For example, the air might be directed by the baffle 174 to pass down the back passages 154 and up the side passages 168, or down one of the passages 168 and up the other passage 168 and the passage 154, or down the passage 154 and one of the passages 168 and up the other passage 168.

DETAILED DESCRIPTION OF FIGS. 4-20 FIGS. 4-20 in which like numerals refer to like elements illustrate the structural details and the airflow patterns of a fireplace constructed according to the principles of this invention of the type which has a single horizontal opening for receiving combustibles. The fireplace assembly is generally indicated by the numeral 10. A firebox generallyindicated as 16 is made up of a base member 20, side walls 18 and 19 and a rear wall 22 which extends vertically upward from the base member 20 until a shoulder 21 is reached from whence the rear wall 22 tapers upwardly and inwardly. The firebox opening is surrounded by fiat elongated frame members 14.

The upper portion of the firebox 16 communicates with a dome structure generally indicated as which in turn communicates with a chimney flue 32. The dome structure 30 is formed from a rear wall 31, a front wall 33, and baffles and 36. The rear wall 31 of the dome structure 30, as best shown in FIG. 6, extends upwardly from the upper end of a rear wall 22 of the firebox 16 to cover member 29 through which the chimney flue 32 is connected to the dome structure and thereby to the firebox by means of a circular opening centrally disposed therein. The front wall 33 of the dome structure 30 extends upwardly from the horizontal opening of thefirebox to the cover member 29. As will be described in greater detail hereinbelow, the walls 33 and 31 form baffles conducting the heated air upwardly and away from the fireplace assembly. Baffles 35 and 36 form the side walls of the dome structure 30, but these walls or baffles extend upwardly beyond the cover member 29, while tapering inwardly, to a cover member 37. A circular opening is centrally disposed in cover member 37 to allow a cylindrical casing 34 which is concentric with but of a greater diameter than chimney flue 32, to pass therethrough. The casing 34 extends downwardly only so far as to pass through cover 37. The annular space between chimney flues 32 and cylindrical casing 34 forms an inner annular duct 40 through which the heated air is expelled to the atmosphere.

A housing 12 entirely surrounds the firebox 16 and the dome structure 30. It will be noted that the portion of the housing 12 which surrounds firebox 16 is substantially rectangular while the walls of the housing 12 surrounding the dome structure 30 taper inwardly forming'a wedge-shaped configuration. The housing 12 is spaced from the walls of the dome structure 30 and the firebox 16 forming therewith the passageways through which the cold air and the heated air circulate around the firebox and dome assembly. A cover member 13 forms the top of the housing 12. Centrally disposed in cover member 13 is a circular opening of a diameter which will allow it to receive a cylindrical casing 38 which extends downwardly only so far as to go through cover 13 and which is concentric with flue 32, but of a greater diameter than cylindrical casing 34. Thus, an annular outer duct 42 is formed between the casings 34 and 38. It is through this outer duct 42 that the cold air for cooling the fireplace assembly 10 is introduced therein.

The housing walls 52 and 54 which are adjacent the dome structure walls 31 and 33, respectively, are inclined at an angle which allow them to be joined with cover members 13 and 37 but not with cover member 29, because walls 31 and 33 are inclined inwardly at a greater angle than the angle of incline of walls 52 and 54 and cover member 29 is narrower. Thus, passages extending from the sides of annular ducts 42 passing down baffles 35 and 36 to the sides of firebox 16 are formed. The rear wall 52 of housing 12 and baffle 31, which is a rear wall of the dome structure 30, form a passage extending downwardly from the annular ducts 40 to the area adjacent the rear wall 22. Likewise, front baffle 33, which forms the front wall of the dome structure 30 and which extends downwardly from the front portion of annular ducts 40 forms along with front wall 54 of the housing 12 a passageway from the upper front portion of the firebox 15 and the surfaces formed by the rear surfaces of vertical frame members 14 to the annular duct 40. The base member 20 of firebox 16 is mounted on legs 15 which extend from the base member 20 to the bottom of housing 12 forming therebetween a .gap 17 which provides a passageway for air flow beneath the firebox. As shown in FIG. 8, an upright baffle 37 is provided which extends downwardly from front to rear within the duct defined by the baffle 35 and the wall of housing 12 adjacent the baffle. Baffle 37 directs a portion of the cool air proceeding down baffle 35 to the front wall 33 of the fireplace dome structure 30. A bafile (not shown) similar to baffle 37 may be provided on the opposite side of the duct at baffle 36. A baffle 39 extending beneath base member 20 directs a portion of the air flow thereunder to rear wall 22.

DESCRIPTION OF OPERATION OF EMBODIMENTS OF FIGS. 4-20 After a fire has been built in firebox 16, as is generally the case with fireplaces having a single horizontal opening, the side walls 18 and 19 of the firebox will be at a lower temperature than rear wall 22, base plate 20 and the front wall 33 of the dome structure. With this temperature relationship of the firebox walls it is desirable to direct the incoming cold air downward along the lower temperature walls allowing the heated air to be drawn upwardly along the walls which are at a higher temperature. This is accomplished by utilizing the principles of this-invention to construct a fireplace assembly of only double-walled construction and providing the appropriate baffles to properly direct the air to and from a counter flow chimney, thus, utilizing the counter flow principle for cooling the exterior surfaces of the fireplace. This should be contrasted with the prior art devices in which triplewalled construction was used to employ thermosyphonic movement of air around the exterior surfaces of the fireplace resulting in a complex, bulky structure.

In operation the cold air is drawn downwardly through outer annular duct 42 and directed by the side baffles 35 and 36 downwardly along the side walls 18 and 19 of the firebox. As mentioned above, baffle 37 shown mounted adjacent side baffle 35 directs a portion of the incoming cold air along the forward wall 33. A portion of the airstream descending adjacent the baffle 36 is directed back up the front wall 33 in a similar manner, as shown by the arrow in FIG. 8. The air directed down the side walls of the firebox will proceed underneath base plate 20 and will be drawn upwardly across rear wall 22 and the rear surfaces of vertical frame members 14. The air directed to the front portion of the fireplace assembly will proceed upwardly along inclined forward wall 33 of the dome structure and enter inner annular duct 40. The heated air from rear wall 22 is directed upwardly along the rear wall 31 of the dome structure into the inner annular duct 40. Therefore, the flow pattern in this embodiment is basically one of having cold air directed down the sides of the fireplace and heated air up the front and back walls.

The fireplace assembly constructed as described hereinabove may be placed in a building wall which provides the necessary clearances. The firebox may be held in place by blocking with stud wall plates or moulding, or it can be nailed or screwed in place through the holes punched in either side of the fireplace frame. Any conventional wall covering material may be applied to the studs providing it does not extend within approximately 2 inches of the sides of the fireplace opening, or within about 4 inches from the top thereof. The chimney may be installed in the conventional manner making sure that the necessary clearances are provided between the chimney structure and the'surrounding wall and floor material.

FIGS. 9-20 are sectional plan views of various fireplace configurations describing the various air flow patterns which may be caused to take place by constructing the particular fireplace according to the principles of this invention. That is,- by providing the particular fireplace configuration with the proper baffles, and by properly placing and directing those baffles, the illustrated flow pattern will be the result. The choice of which baffle configuration to use will depend upon which walls are desired to be kept at a lower temperature with respect to the other walls.

FIGS. 9-12 illustrate the flow patterns which may be caused to occur in an open front fireplace like the one described hereinabove as a preferred embodiment of the invention. FIG. 9 is a diagram of the flow pattern taking place in the fireplace assembly described hereinabove with reference to FIGS. 4-8. The baffles direct the cold air down theside of the fireplace and up both the front and the back. FIG. 10 demonstrates a variation of the flow pattern in the same type of fireplace wherein air is caused to move down the sides and front of the fireplace and up the back. Alternatively the baffle arrangement can cause the air to move down the sides, but the air from one side moves only up the back wall while the air from the other side moves only up the front. FIG. 11 illustrates an open-front fireplace in which the air flow pattern of FIG. 9 is just reversed. In this case the air is caused to move down the front and back and up the side walls. FIG. 12 is a flow pattern which is just the reverse of the flow pattern of FIG. 10, and in this case the air moves down the back and up the sides and front. Alternatively the baffle arrangement can cause the air to move down the front and back, but the air from the back moves only up one side and the air from the front moves up only the other side.

FIGS. 13-16 illustrate the flow patterns which may be caused to occur in the fireplace having two adjacent sides open, and indicated by the legend openings and the arrows. In these figures the same sequence of flow patterns as was illustrated in 1-12 may be caused to take place.

FIGS. 17-20 illustrate the use of this invention in conjunction with a see through fireplace or one in which two opposite sides are open. The sequence of the flow pattern in these figures is the same as the sequence illustrated in FIGS. 9-12. v

The embodiments described hereinabove are only I exemplary, and it will be apparent to those skilled in the art that the construction and arrangement of the elements of the invention maybe modified within the scope of the appended claims.

What is claimedis:

l. A fireplace assembly comprising a lower firebox portion defining a hearth opening and having upper and lower horizontal bottom walls defining a hearth floor and a horizontal space therebelow, inner and outer walls extending upwardly from the edges of the floor and defining a plurality of vertical passages adjacent the hearth opening and having their lower ends in communication with said horizontal space, said inner walls forming a dome portion above the hearth opening and terminating in a vertically extending smoke pipe, said outer walls extending upwardly and surrounding the dome portion in spaced relationship to the dome portion, means defining annular cooling air inlet and outlet openings surrounding the smoke pipe, and baffle means disposed in the space between the dome portion and the'outer walls and adjacent the inlet and outlet openings for directing air from the inlet opening down at least one of said passages so as to flow into said horizontal space below the hearth floor and then up one of the other passages, said baffle means directing the upflowing air to said outlet opening.

2. A fireplace assembly comprising a lower firebox portion defining a hearth opening and having inner and outer rear walls defining a rear passage, two sets of inner and outer side walls defining two vertical passages, one on either side of the hearth opening, upper and lower bottom walls below the hearth opening defining a floor and a space which is in communication with the lower end of the rear passage and with the lower end of each side passage, said inner walls extending upwardly to form a dome portion and terminating in a vertically extending smoke pipe, said outer walls extending upwardly and surrounding the dome portion in spaced relationship to the dome portion, means defining annular cooling air inlet and outlet openings surrounding the smoke pipe, and baffle means disposed in the space between the dome portion and the outer walls and adjacent the inlet and outlet openings for directing air from the annular cooling air inlet down at least one of said passages so as to flow into said bottom space and then up at least one of the other passages, said baffle means directing the upflowing air to said annular outlet opening.

3. A fireplace assembly as in claim 2 wherein said one passage through which air flows downwardly is provided with thermal insulation on the walls nearest the firebox to reduce heating of the down air, and wherein said other passage through which air flows upwardly is free of insulation on the walls nearest the firebox so that up air is heated more than down air to increase thermosiphonic flow of air through said passages.

4. A fireplace assembly as in claim 2 including a heat shield disposed generally parallel to and spaced from each side wall just above the hearth floor, each shield defining with its respective side wall a space which is open along a vertical edge at the front of the hearth opening and open along a horizontal edge at the top of the hearth opening whereby room air may enter said space and pass upwardly into the dome portion in order to prevent overheating of the respective side wall.

5. In a fireplace assembly, an outer cabinet and an inner firebox and dome structure terminating at its upper end in a smoke pipe, the cabinet having an opening at the top surrounding the smoke pipe and having walls defining spaces with the rear, sides and front of the dome and with the rear, sides and bottom of the firebox; baffle means within the outer cabinet forming an opening surrounding the smoke pipe, said baffle means having walls extending downwardly from said opening in spaced relationship to the dome and the cabinet, said walls having lower edges closing with the lower portions of the front and sides of the dome and having rear edges closing with the inner surface of the cabinet adjacent the dome to thereby form an outer space adjacent the cabinet and an inner space adjacent the dome.

6. A fireplace as in claim 5 including interior walls located between the cabinet and the firebox and dome structure dividing the spaces adjacent the sides and rear of the firebox into a vertical rear passage and two vertical side passages, said passages being sealed from each other and having lower ends communicating with the space defined by the cabinet and the bottom of the firebox, said rear passage having an upper end communicating with said inner space formed by said baffle. 

1. A fireplace assembly comprising a lower firebox portion defining a hearth opening and having upper and lower horizontal bottom walls defining a hearth floor and a horizontal space therebelow, inner and outer walls extending upwardly from the edges of the floor and defining a plurality of vertical passages adjacent the hearth opening and having their lower ends in communication with said horizontal space, said inner walls forming a dome portion above the hearth opening and terminating in a vertically extending smoke pipe, said outer walls extending upwardly and surrounding the dome portion in spaced relationship to the dome portion, means defining annular cooling air inlet and outlet openings surrounding the smoke pipe, and baffle means disposed in the space between the dome portion and the outer walls and adjacent the inlet and outlet openings for directing air from the inlet opening down at least one of said passages so as to flow into said horizontal space below the hearth floor and then up one of the other passages, said baffle means directing the upflowing air to said outlet opening.
 2. A fireplace assembly comprising a lower firebox portion defining a hearth opening and having inner and outer rear walls defining a rear passage, two sets of inner and outer side walls defining two vertical passages, one on either side of the hearth opening, upper and lower bottom walls below the hearth opening defining a floor and a space which is in communication with the lower end of the rear passage and with the lower end of each side passage, said inner walls extending upwardly to form a dome portion and terminating in a vertically extending smoke pipe, said outer walls extending upwardly and surrounding the dome portion in spaced relationship to the dome portion, means defining annular cooling air inlet and outlet openings surrounding the smoke pipe, and bafflE means disposed in the space between the dome portion and the outer walls and adjacent the inlet and outlet openings for directing air from the annular cooling air inlet down at least one of said passages so as to flow into said bottom space and then up at least one of the other passages, said baffle means directing the upflowing air to said annular outlet opening.
 3. A fireplace assembly as in claim 2 wherein said one passage through which air flows downwardly is provided with thermal insulation on the walls nearest the firebox to reduce heating of the down air, and wherein said other passage through which air flows upwardly is free of insulation on the walls nearest the firebox so that up air is heated more than down air to increase thermosiphonic flow of air through said passages.
 4. A fireplace assembly as in claim 2 including a heat shield disposed generally parallel to and spaced from each side wall just above the hearth floor, each shield defining with its respective side wall a space which is open along a vertical edge at the front of the hearth opening and open along a horizontal edge at the top of the hearth opening whereby room air may enter said space and pass upwardly into the dome portion in order to prevent overheating of the respective side wall.
 5. In a fireplace assembly, an outer cabinet and an inner firebox and dome structure terminating at its upper end in a smoke pipe, the cabinet having an opening at the top surrounding the smoke pipe and having walls defining spaces with the rear, sides and front of the dome and with the rear, sides and bottom of the firebox; baffle means within the outer cabinet forming an opening surrounding the smoke pipe, said baffle means having walls extending downwardly from said opening in spaced relationship to the dome and the cabinet, said walls having lower edges closing with the lower portions of the front and sides of the dome and having rear edges closing with the inner surface of the cabinet adjacent the dome to thereby form an outer space adjacent the cabinet and an inner space adjacent the dome.
 6. A fireplace as in claim 5 including interior walls located between the cabinet and the firebox and dome structure dividing the spaces adjacent the sides and rear of the firebox into a vertical rear passage and two vertical side passages, said passages being sealed from each other and having lower ends communicating with the space defined by the cabinet and the bottom of the firebox, said rear passage having an upper end communicating with said inner space formed by said baffle. 